Abstract Background and Aims Serum chloride is an emerging marker of mortality in patients with hypertension, heart failure, sepsis, and chronic kidney disease. The causes of this finding are still unknown, although it is suggested that both haemodynamic and inflammatory factors may play a role. On the other hand, Neutrophil-to-lymphocyte ratio (NLR) and platelet-to-lymphocyte ratio (PLR) have been found to be associated with increased inflammation in various cohorts. Method Retrospective cohort study. We analysed data from 558 patients who underwent cardiac catheterization at our hospital between June and October 2022. Baseline, pre- and post-procedural analytical data, as well as concomitant treatment were obtained (Table 1). Results The mean age was 65.89 years. Women accounted for 31.2%. 40.9% had diabetes, 71.9% had hypertension, and 21.9% had ischaemic heart disease. Pre-procedural serum creatinine (Crs) was 1.08 mg/dl (±0.44). Patients with pre-procedural hypochloremia (defined as serum chloride levels less than 98 mEq/L) had higher NLR (5.89 vs 3.6) (p = 0.002) and PLR (139.44 vs 132.08) (p = 0.009). This relationship was maintained in the post procedure analysis. (Table 1 and Fig. 1). Conclusion In our sample, the presence of hypochloremia (serum chloride levels below 98 mEq/L) was associated with higher NLR and PLR levels both pre and post cardiac catheterization.